Approximately 1 million people in the United States suffer from cartilage injuries every year. Traumatic knee injuries, often seen in otherwise healthy, active patients, commonly result in focal cartilage defects of the weight bearing articula surfaces of the knee. These defects can be sometimes asymptomatic, but swelling, pain and instability of the joint may occur. In addition, chronic degeneration of the cartilage due to alterd joint mechanics and loading may predispose the patient to the development of premature osteoarthritis (OA). Recent studies in the development of disease-modifying OA drugs (DMOADs) and cartilage repair therapies (bone marrow stimulation, tissue and cell-based techniques) are promising for the future management of disease. Ideally, any cartilage repair procedure would result in the regeneration of hyaline cartilage that has morphological, mechanical and biochemical properties similar to those of native cartilage. Therefore, there is a significant need for reliable, non-invasive MR biomarkers that could detect the early biochemical changes in cartilage even before morphological changes occur or in-vivo monitoring of cartilage repair procedures. The overarching goal of this proposal is to develop the hardware (dual tuned 23Na/1H knee coil array) and software (3D-FLORET-23Na- techniques) for in-vivo knee imaging on standard 3T clinical scanner. High- resolution, 23Na-(aggrecan) and 1H-(morphology, collagen) imaging of cartilage, along with improved RF coils, novel pulse sequences, image reconstructions, and visualization methods on 3T, will significantly improve the ability of clinicians to objectively monitor the efficacy of cartilage repair procedures. The proposed techniques developed will allow orthopaedic and trauma surgeons cutting-edge, powerful, noninvasive tools for diagnosis, pre-operative planning, and postoperative monitoring of cartilage repair through biochemical MRI. The outcome of this proposed study will significantly impact our ability for personalized treatment regimens and possibly prevent the development of premature OA.